Hydraulic weighing scale



April 3, 1948. L. s. WILLIAMS 2, 89,533

HYDRAULIC WEIGHING SCALE Filed Sept. 6, 1944 3 sheets-sheet 1 INVENTOR. Lawrence 5. MW/ams MZZQQWM ATTORNEYS April 13; 1948.

L. SQWILLIAMS HYDRAULIC WEIGHING SCALE Filed Sept. 6, 1944 s Sheets-Sheet 2 JNVENTOR. Lawrence 5. W/'///'ams BY 2 ATTORNEYS April 13, 1948. s. WILLIAMS HYDRAULIC WEIGHING SCALE 3 Sheets-Sheet 3 Filed Sept. 6, 1944,

I N V EN TOR. L aW/"ence 5. W/W/ams MZZZ ATTORNEYS Patented Apr. 13, 1948 2,439,533

UNITED STATES PATENT OFFICE HYDRAULIC WEIGHING SCALE Lawrence S. Williams, Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio, a corporation of New Jersey Application September 6, 1944, Serial No. 552,865

This invention relates to force transmission mechanism and in particular to a device for precisely translating hydraulic pressure into mechanical force. The force translating mechanism embodying the invention is primarily designed for use in the receiving end of a hydraulic scale system and serves to translate hydraulic pressure produced by loads on a load receiver into mechanical force which is counterbalanced and indicated by weighing mechanism.

In the construction of hydraulic weighing scales of high accuracy, it was found that the bellows used at the receiving end of the hydraulic system was responsible for a large portion of the errors observed. From an analysis of the errors it appears that the eifective area of the bellows varies with the magnitude of the load or force being translated. The apparent variations in effective area, instead of bein proportional to the force being transmitted, are greater during the application of the first part of the load than they are during the application of the remainder of the load. It is thus impossible to correct for these variations by changes in lever ratio or poise weight.

The object of this invention is to provide a simple mounting for a bellows used in a force translating system which inherently compensates for the error introduced by the bellows.

Another object of the invention is to provide means which, while allowing deflection of a bellows mounting along the axis of the bellows, prevents any twisting or angular movement of the bellows mounting.

A still further object is to provide a freely rockable connection between a bellows sealing member and a strut which transmits force thereto.

These and other objects and advantages are attained in the examples shown in the drawings which illustrate preferred embodiments of the invention.

In the drawings:

Figure I is an elevation, partly in section with some parts broken away, of a hydraulic weighing scale embodying the invention.

Figure II is a fragmentary plan of the receiving end of the hydraulic system of the weighing scale shown in Figure I,

Figure III is a side view, partly in section, of the receiving end of the hydraulic system.

Figure IV is a greatly enlarged sectional view of a pressure receiving unit embodying a. form of the invention.

7 Claims. (Cl. 265-47) for supporting the lower end of the bellows of the Figure V is a plan view of a diaphragm used pressure receiving unit shown in Figure IV.

Figure VI is a vertical section of one of the pressure receiving units of the receiving system shown in Figure III.

Figure VII is a plan view of a diaphragm assembly used in the pressure receiving unit shown in Figure VI.

Figure VIII is a fragmentary vertical section taken along the line VIII-VIII of Figure VlI.

Figure IX is a fragmentary vertical section taken along the line IXIX of Figure VII.

Figure X is a plan view with parts broken away showing an alternative form of diaphragm for supporting the pressure receiving bellows.

Figure XI is a fragmentary vertical section taken along the line XIXI of Figure X.

Figure XII is a plan view with parts broken away showing still another form of diaphragm 1 assembly.

Figure XIII is a fragmentary vertical section taken along the line XIII-XIII of Figure XII.

Figure XIV is a plan view with parts broken away showing still another form of diaphragm assembly.

Figure XV is a fragmentary vertical section taken along the line XV-XV of Figure XIV.

These specific drawings and the accompanying description disclose a preferred embodiment of the invention and are not intended as a limitation of the claims.

Fundamentally, the invention consists in resiliently mounting one end of a bellows used in a hydraulic force transmission system so that the deformation of the mounting under loadwill produce a mechanical deformation of the bellows in such direction and magnitude that the elastic forces generated in the bellows thereby will compensate for changes in effective area of the bellows. It has been found that when a bellows is installed in a cup-shaped housing and hydraulic fiuid is admitted to the space between the housing and the bellows, thus tending to compress the bellows, the effective area of the bellows decreases at a decreasing rate with increase in hydraulic pressure. When such a structure is used in a weighing scale the apparent area change causes the scale to be slow at half capacity, i. e. indicate less than the actual load, when it is adjusted to indicate correctly at full load. By providing a resilient mounting between the bellows and the cup-shaped housing, the deformation of the mounting tends to stretch the bellows and thus aid in transmitting force to the lever system. By employing an'annular diaphragm as the resilient member a nonlinear force-deflection ratio is obtained, the nonlinearity being in such direction as to correctly compensate for the error inherent in the bellows.

A complete hydraulic scale comprises a rectangular load receiving deck I supported on longitudinally extending girders 2. At each cornor of the deck I* the girdersnz v are" supported" on a depending-bracket} the bottom of which provided with a horizontal crossbar 4 engaging 10 a link 5 suspended from a crossbar 6 spanning; the space between the sides of anopen-endedbox-like member I.

The space between the recessed member 9 and the upper member ID is filled with a hydraulic-. fluid, the hydraulic fluid being'retained by a flexible yet nonstretchable diaphragm ll. ThGJJ'OX-I- like member I and the upper plate In of the capsule 8. are prevented: from tipping, bystabilizer: rings 12' surrounding the box like members T and bolted to theupper plates Illr The-ringsEIZ, one for each ofthe capsules supporting. the load receiver, are joined by an Heshapedvpipeand I-beam. framework l3 which, while not designed to carrysany. of the. load .on. the" deck, .serves .tohold the upper plates of the capsules fl in' perfect alignment. Horizontal oscillation of the deck- I 'in response 'to movements of loads is.per-' mitted. by. the-swinging action of the links: without'producingianydeformation of the hy-- draulic capsules 8;

Loads placed on the-deck! aressupportedby hydraulic pressure in thecapsules. 8. The hy 55 draulic pressure from. each ofvthe capsulesis transmitted through one of: a .series' of tubes I4 toa pressure receivingunit, l5 mounted-=on :a pedestal l6- erectedfrom a .base-l1.- Aseries of struts [8 extending upwardly into the pressure w;

receiving units l5-transmit force to a'j'leverlil fulcrumed on stands erectedfromthebaseJ I. The. lever: l9 extends-between spaced: apart legs of-the pedestal l6 and:at'itsniar-end is-pivotally:

engaged by a stirrup 2| depending from a: steels- 4-5 1 yard rod 22 supported-e from 1 a: ,load'1-pivot-- 23 of a weigh beam 24. The Weigh-tbeam=24 is,-ful.- crumed on afulcrum.- stand: 25* erected from, a weigh beam shelf? 25 which inturn is supported.

on pipe stands 21- an'd 28. A poiser29rslidably; 501

mounted on the weigh beam 24 ;servesz-t'o' coun-' terbalance loads applied throughathesteelyard rod As shown in Figure -II,;,the lever=xl9; substantially in the form ofanwA; has fulcrum-:pivots':

at the-end of its legs and apower.npivotaataits: apex. The pressurereceivinggunits [5,;onefor each of'the four capsules 8,= are ;disposed in arrow above. the crossbar of the A.=- In this :arrangement the mechanical --forces-producednby the .hy 6'0 draulic transmission .systems are added. together by the lever I 9;

Referring. .to Figure. III,. hydraulic. pressure." from the capsule is transmitted throughi-the.tube;

I4" to. the interior of .La :cup-rshaped. housing-:30

constituting :the .stationarypart ofi the pressure receiving unit l5.- The housing-rlio'rhaszaxflange; 3| extending ..longitudinally .alongioneside. The: ends of-- the fiange 31 are flarednoutwardly. so

that when the housing;3011s:mounteds:.on -the pedestal Iii-with the sidesof thexflange' 31 ycone tacting *-vertical machined surfaces -32 of thepe'd A estal I 6 a pair .ofiCOIlG pointed screws 33 threaded throughrhorizontal. flanges. 34. oil the pedestal. J 63 The box-like'member T is' supported by a hydraulic capsule 8 comprising-1a recessed bas member 9 and". amupperficplatezlllf .inzline with the knife edge and to the knife edge .block .38 at. points remote from the line of the knife" edge. The knife edge blocks 33 are mounted -inia row in the lever l9 and are each individually adjustable to vary the respective pivot distances This adjustment, which is made bya selective tightening of a pair of cone pointed screws 4i'lcontactin the ends of the knife edge 'blockr38," is used to adjust the overall force transmission ratio from each corner of the scale and thussecurecorrect Weighing of loads regardless of their position on the scale.

ReferringtoFigure IV, thebellowsfi substantiallyfills the space within the cup-shaped housing fifl. Hydraulic fluid entering the housingithrough an opening 4| from one of the tubes l4fil1s thespacebetween the bellows and. the housing. The lower end of the bellows 35 is sealed'to a sealing ring42. Theinner edge of an annular diaphragm 43 is clamped against ashoulder l i of the sealing ring 42- by a clamp ring threaded-onto the lower portion ofthe sealingringflz. Theouter edge of the annular diaphragm 434s clamped into-the bottom of the housing 30 by a threaded locking ring 45.

When hydraulic pressure 'is applied in the space between-the housing 30 and the bellows 35, it

acts downwardly-on the top of the bellows sealing cap 36.-and that force is transmitted throughthe strutl8-to the counterbalancing lever system.

Thepressure also acts onthe sides of the bellowsand between. its 'iolds; The." effect of the pressure appliedto the, bellows appears: to be a slightreduction" in effective cross-sectional area-ofthe bellows thus causing the translation ratio'be-- tweenlhydraulic pressure and mechanical force tochangewith loadn The-bellows 35 is: madeof a metallic elastic.

material and acts as a-spring in resisting any deformation. Thus, if the lower-end ofthe bellows: is pulled downwardly as hydraulic load isapplied, ant-additional force is transmitted to the strut I8 2 which may: be used to compensate for the apparent decrease in cross-sectional area. The-hydraulic. pressure acting against thediaphragm 43which initself is a nonlinear: elastic-- member; slightly deflectsrth'e diaphragm and thus stretches the bellows to cause the springeffect of: the bellows: to: supplement the. forcestransmission. of the zhydraulic pressure acting against the bellowscap 36:" By suitably proportioningtthe area, the thickness and the elastic modulusof the annular diaphragm, it can: .b'eimade to nonlinearlyastretch the-:bellcws and: thus completely compensate for the nonlinear change :in apparent effective area.

The; amount of. stretching; required .to efiect compensation isrslight; Inorder.totsecureefietn tive compensation the annularfdiaphragml ts and the bellows sealingming .112 must'notibe allowed to twist tor-rock; about a? horizontal axis Such rocking; .by-iintroducing other forcesinto the diaphragm 1 43;. produces: greater errors than those which the diaphragm is designedto I remove.

mayiengagexandzadjustablyz lock itlie flanee 3l in '75 'l'h erefore; in-the practical form of pressure-meceiving unit used in the scale shown in Figure I and, in detail in Figure VI, the diaphragm comprises upper and lower members 41 and 48 which together act as a parallelogram to ensure pure axial motion of the bellows sealing ring 42. In the construction of the composite diaphragms formed of the annular diaphragms 41 and 48, the individual diaphragms are spot welded to a pair of spacing members 49 and 50. It is not necessary that they be continuously welded inasmuch as a liquid tight seal is not required between the diaphragms and the spacing rings. Hydraulic fluid is prevented from escaping past the diaphragms by a pair of gaskets 5| and 52. The welding, however, prevents any radial slipping of the diaphragms 41 and 48 when load is applied. If such slipping were allowed, it would introduce friction into the weighing and would show up as a difierence in weighing as loads are applied or removed.

It is also desirable, to secure the best force-deflection curve to prevent the diaphragm 41, which is exposed to the hydraulic fluid, from taking on a curved dished appearance as the pressure is increased. It is desirable that the flexure in the diaphragm occur near its supported edges and that when deflected it forms a very shallow cone. The diaphragm may be stiffened by providing short radial dimples 53. These dimples serve to stifien the unsupported portion of the annular diaphragm 41 without materially increasing its resistance to deflection of the bellows sealing ring 42.

It is possible to secure very nearly correct compensation of the bellows error without providing the dimples 53. Thus, the diaphragm assembly shown in Figure X, which comprises an upper flat annular diaphragm 54, a lower diaphragm 55 and spacing rings 56 and 5'|,'may be substituted for the composite diaphragm having the dimples without materially changing the operation or the accuracy of translation of the hydraulic pressure to mechanical force.

It may be found with available diaphragm materials that the flat diaphragms 54 and 55 are too stiff and insufficient compensation is obtained. If this occurs, a perforated diaphragm 58 may be substituted for the lower diapragm 55. The diaphragm 58 has a series of arcuate holes 59 out through it leaving radial spoke-like portions 60 which serve to guide the bellows sealing ring 4'2 but which do not ofier material resistance to axial motion. It is also immaterial, except for sealing in the hydraulic fluid, whether the diaphragm 58 is installed as the upper or the lower diaphragm in the assembly. If it is installed as the upper diaphragm, the hydraulic fluid, of course, fills the space between the diaphragms and suitable gaskets must then be used below the diaphragms to prevent the escape of the fluid.

If, on the other hand, it is found that the diaphragm assembly, shown in Figure X, allows too much deflection of the bellows ring 42, the upper diaphragm 54 may be replaced by a reinforced diaphragm 6 I. The diaphragm 6| has an annular plate 62 welded to its lower surface. The annular plate 62 extends radially nearly the full distance between the spacing rings 56 and 51 to which the upper and lower diaphragms are welded. Sufficient radial space is allowed between the spacing rings 56 and 51 and the annular plate 62 to allow the diaphragm 6| to bend under the influence of the hydraulic pressure.

These are representative of a number of ways in which a bellows may be resiliently mounted so that it is mechanically stretched in accordance with the hydraulic pressure. In a co-pending application Ser. No. 523,669 (now Patent No. 2,379,207) a similar result is obtained by installing an internally stressed bellows in the strut 18, the internally stressed bellows acting to lengthen the strut [8 in proportion to hydraulic pressure, thus in effect, stretching the bellows. The diaphragm assemblies, disclosed in this application, accomplish the same result by moving the normally rigidly supported end of the bellows.

In the interest of securing the greatest accuracy from the bellows, it is desirable that the top of the bellows, the end sealed by the cap 36, be free to assume whatever position it will. In order to allow it substantially frictionless freedom and yet retain stability, the bellows cap 36 is made with a central boss 63 extending considerably higher than the point of attachment of the bellows 35. The interior of the boss 63 is bored, the end of the bore terminating in a conical recess 64. The vertex of this conical recess lies on the axis of a cylindrical surface 65 to which the bellows is attached. The vertex, however, is disposed in a plane above the surface 65 such that when hydraulic pressure acts downwardly on the cap 36 it will, in effect, hang suspended on a rounded conical point 66 of the strut l8. Inasmuch as the bellows attempts to contract under the influence of hydraulic pressure, it acts an a tension link pivotally connected to the strut i8 and the housing 36. The strut I8 is much longer in length, therefore, any side deflection or tendency to tip of the bellows immediately produces a restoring force tending to return the bellows and strut to their midposition. Thus, although the strut I8 is pivoted at each end and the bellows 35 is resilient, a stable structure is obtained because the application of hydraulic pressure tends to force these elements into their correct positions. If the upper end of the bellows is restrained by making a rigid connection between the bellows cap and the strut, the efiect of small irregularities or inaccuracies in the bellows will be magnified and show up as errors in the scale indication. The pivoted connection, by allowing the bellows to freely move equalizes these inaccuracies and thus produces an accurate frictionless translation of hydraulic pressure to mechanical force.

Having described the invention, I claim:

1. In a device of the class described, in combination, a housing having a recess connected to a source of hydraulic pressure, an elastic bellows mounted in said recess, means for sealing the inner end of the bellows and transmitting force from said bellows, and a resilient mounting for supporting said bellows and sealing the space between said bellows and the mouth of said recess, said resilient means comprising a pair of spaced annular diaphragms, one of which is subjected to hydraulic pressure.

2. In a device of the class described, in combination, a housing having a recess connected to a source of hydraulic pressure, an elastic bellows mounted in said recess, means for sealing the inner end of the bellows and transmitting force from said bellows, and a resilient mounting for supporting said bellows and sealing the space between said bellows and the mouth of said recess, said resilient means comprising a pair of spaced annular diaphragms, one of which is subjected to hydraulic pressure and has means for preventing bulging under the influence of pressure.

3. In a device of the class described, in comc eeses v bination, a housing havinga recess connected to a source of hydraulic pressure,- an elastic r-bellows mounted in said recess-means for-sealing the inner end of the bellows and transmitting force from said bellows, and a resilient mounting zfor supporting saidbellows and sealing the space between-said bellows and the mouth "of said-recess, said resilient means com-prisingna pair of spaced annular diaphragms, one of which is subjected to hydraulic pressure and the other of which is perforated to reduce its axial stiffness without decreasing its radial stifiness.

4. In a device: of the class described, in combination; a housing having -a'recess connected to a'source of hydraulic pressure, an elastic bellows mounted in said. recess; means for sealing the innerjend of the :bellows and transmitting force from said: bellows, and a resilient mounting for supporting said bellows 'and sealing the. space between said bellows-.andthe mouth'of said recess, said resilient meanscomprising a .pair'of spaced annular diaphragma-one of which is .subjected to hydraulicupressure and; is 'reinforced'by a thin metallic'annular plate box-resist. curved deformation.

: 5. In adevice of theclassdescribed; in combination, a housing having. a recess .connecte'dzlto a source of'hydraulic pressure, ;an elastic bellows mounted in said recess; means for sealing the inner end of the bellows-and itransmitting 1 force from: said bellows, and :a resilient mountingfor supporting said bellowsand sealin the spacehetween-said bellows and the mouth ofsaidlrecess, said resilient. means comprisinga pair Ofi'SPaCEd annular diaphragms,--one :of which" is subjected to hydraulic pressure and: is provided with apluralityof radial dimples to resist curvedideformation.

6. In a device of theclass described,:.in:;combination,- a hydraulic" capsule serving asi-aisupport for a load-receiver, a housinghaving-aarecess therein, a hydraulic connection between the capsule an'd the recess, a bellows contained in the recess,-a' resilient-annular diaph'ragm'fixed in the mouthof the recess -and-=sealed to the adjacent end of the "bellows, means for sealing the other end of the be'llows and transmitting force therefrom, guiding means engaging the adjacent end :of' the' bellows for maintaining the end of the bellowswhen deflected in parallelism with its nondefiected position, said diaphragm having a pressure'deflection characteristic that permits move- :ment of the attachedend of the bellows to correct errors *in v force I translation of the bellows and capsule.

"7."In a deviceof the class described, in combination a housing having a recess therein, a hydraulic connection between. a source of hy- Idraulic pressure and the recess, a bellows contained inthe recess, -a"resi-1ient annular diaphragm fixed in the mouth of the recess-and supportingthe adjacent end of the-bellows, means for sealingthe other end of-the bellows and transmitting force to a forcecounterbalancing mechanism, means engaging the adjacentend of the bellowstor maintaining the end of the bellows when deflectedin parallelism with its non-deflected position, said diaphragm serving to stretch the-bellows-accor'ding to the" hydraulic pressure and thereby-transmit additional iorce to the force counterbalancing mechanism.

LAWRENCE S. WILLIAMS.

REFERENCES CITED The'followingreferences are of. recordin the file-of this patent:

- UNI'I'ED STATES PATENTS 

